Tuning system



April 17, 1926. 1,666,685

N. H. CLOUGH TUNING SYSTEM Filed April 15, 1926 INVENTQ NEWSOMEHENRY UGH BY 9 4 /dddae AT RNEY Patented Apr. 17, 1928.

UNITED STATES 1,666,685 PATENT omcs.

BURY CLOUGH, OI OBELIBIOBD, ENGLAND, LBSIGNOB '10 RADIO B- POBATION OI ERICA, A CORPORATION OF DELAWARE.

TUNING BYSTEI.

Application fled April 18, mo, Serial Io.

provide variable tuning means such as va-- riable inductances which I by rotation through a range of 180 cover a given band.

of frequencies and their corresponding wave lengths. It has been customary also 1n cer- 29 tain instances to provide separate switching means for insertingor removing additional impedances in the resonant circuit, whereb other frequenc bands may be receive This, however, has been found awkward because of the necessity for the additionall manipulation of controls and the added complexit It 18 often desirable to provide for the rece tion on a single tuning device of two I 80 ban 5 of wave-lengths, separated by an interval (erg. 300-500 metres, and waves in the vicinit vantages 0 using, for this purpose, a tuning device with a high ratio of maximum to ength, continuously va-' minimum waveriable between these limits (e. g. a seriesparallel variometer), are (a) desired waveengths are crowded together on two portions of the scale, the rest of which is oo- 40 cupied b wave-lengths not desired, and

(b) the difliculty of providing approximately equal sensitivity at maximum and minimum. When app ying my invention, however, these disadvantages are no Ilonger prescut and the whole 360 of tuning scale may be usefully employed.

According to my invention I provide. the

rotatable element of a tuning device with a switch or switches, adapted automatically .50 to include or exclude a loading device or devices from the circuit of the said tuning device in series or in parallel therewith.

The tuning device may take the form of a variable inductance, such as a variometer 66 or a variable condenser, and the loading deof 1600 metres). This disad-- roam, and in Great 3mm April 24, 1028.

vice may be a fixed inductance or a fixed condenser. p In one form of construction, the variable tuning and loading device comprises a tuning device of the kind in which full variation is effected on rotation of the rotatable element through 180, and a switch which, after the said rotatable element has been rotated through 180,- automatically includes in series with the tuning device a loading device, so that on continued rotation of the rotatable element through a further 180, full variation of the tuning device will again be effected, but over a different range. After the rotatable element has been rotated through 360, the loading device is again automatically cut out.-

By this means convenient reception of signals lying within two separate frequency bands is possible.

Other objects and structural details of my invention will be apparent from the following description w en read in connection with the accompanying drawing, wherein:

Fig. 1 is a view in elevation of the ap paratus of my invention.

Figs. 2, 3, 4, 5, and 6 are diagrammatic representations, of circuits adapted to employment with the device of my invention.

Referring to Figure 1, L is a coil whose inductance can be varied by rotating a copper ring R, which is mounted within the coil upon a s indle S. Also mounted upon the spindles is an insulated exam 0, so shaped that, throu h 180 of rotation of the ring R, it presses t e switch tongue T away from a contact upon the plate Q; while during the other 180 of rotation, it permits the tongue T to make contact- The switch T;-Q serves in its closed position to shortcircuit an additional external inductance connected in series with the coil L.

The electrical arrangement is shown diagrammatically in Figure 2, in which the switch Q-T is represented by a doublewe headed arrow.

The invention may be employed to include or cut out any kind of loading device or leading devices, and, if desired, more than one switch may be provided. For example, 106 in the arrangement shown diagrammatically in Figure 3, in which an extra inductance and an extra capacity are emplo ed for loading a variometer, two switches and Y are provided, and are so arranged that X opens 110 when Y closes, and vice versa. In this figare, the variometer is represented b a variable inductance, and the additiona inductance by a fixed inductance. The full-line capacity represents the additional capacity,

while the dotted-line capacity represents the capacity of the rest of the circuit (e. g. an aerial-earth capacity).

Figure 4; shows diagrammatically a meth od cf loading avariable condenser with inductance and capacity. The arrangement is analogous to that shown in Figure 3, the switch X opening when the switch Y is closed and vice versa. The dotted inductancerepresents the inductance of the coil originally in the circuit.

Figures 5 and 6 show diagrammatically an arrangement for loading an ordinary two-coil variometer with an additional coil. The coils of the variometer are represented by the arrow-linked inductances.

In' the arrangement shown in Figures 5 and 6, the dotted capacity represents the capacity of the rest of the circuit. The cam C, which'operates the switches, is, of course, electrically conductive, and the switch is so designed'with respect to the said cam that the inductance of the circuit is increased for rotation of the spindle in the same direction in both positions of the said switch.

Z is a loading inductance of large value compared with that of a half winding of the variometer, so that when the apparatus is in the position shown in Figure 5, the shunting effect*-of the inductance Z upon the upper variometer coil is negligible.

In the position shown in Figure 6, the inductancefis connectedin series with the variometer,. v V

By the system of my invention I am enabled to provide a convenient tuning system adapted touse over two or more separate frequency bands under the actuation of a single control 'and indicating device.

While I-have shown but one embodiment of my invention in the foregoing drawings and description it is capable of various mod fications therefrom without departing from w the spirit thereof and, it is desired therefore that only such limitations shall be imposed thereon as are required b the prior art or indicated by. the appende claims. I claim as my invention:

1. In a resonant-circuit 'a variometer, a

.fixed inductance, and a switch cooperating with said variometer and actuated thereby, adapted to include or exclude said fixed inductance from said resonant circuit.

2. A variable impedance comprising a two coil variometer, an impedance element, and a switch for connecting said impedance ele-; ment in series with said variometer and in parallel with one of the coils of said vari' ometer.

3. A variable impedance comprising a two coil variometer, an impedance element, and

a switch for connecting said impedance element in serieswith said variometer during one half of the rotation of said variometer,,

and in parallel with one of the coils of dance element in series with sai variometer.

during half of the rotation of said variometer and in parallel with one of the coils of said variometer during thev remainder of the rotation of said variometer.

5. A variable impedance comprising a two coil variometer, an inductance member, and

a switch cooperating with said variometer and actuated thereby for connecting said inductance element in parallel with one of the coils of said variometer during part of the rotation of said variometer and in serieswith said variometer during the remainder of the rotation of said variometer.

o. A variable impedance comprising a two coil variometer, an inductance member, and

a switch for connecting said inductance member in series with said variometer during one 'half of the rotation of said variometer and in parallel with one of the coils of said variometer during the other half of the rotation of said variometer.

NEWSOME HENRY GLOUGH. 

